For purposes of this discussion, an RFID transponder generally comprises a substrate, an RFID chip or chip module (CM) disposed on or in the substrate, and an antenna disposed on or in the substrate. The transponder may form the basis of a secure document such as an electronic passport, smart card or national ID card, which may also be referred to as “data carriers”. The chip (CM) may be also referred to as an integrated circuit (IC).
The RFID chip (CM) may operate solely in a contactless (non-contact) mode (such as ISO 14443), or may be a dual interface (DI, DIF) chip module (CM) which may additionally be operative to function in a contact mode (such as ISO 7816-2) and a contactless mode. The RFID chip (CM) may harvest energy from an RF signal supplied by an external RFID reader device with which it communicates. The chip module (CM) may be a leadframe-type chip module or an epoxy-glass type chip module. The epoxy-glass module can be metallized on one side (contact side) or on both sides with through-hole plating to facilitate the interconnection with the antenna.
The substrate, which may be referred to as an “inlay substrate” (such as for electronic passport) or “card body” (such as for smart card) may comprise one or more layers of material such as Polyvinyl Chloride (PVC), Polycarbonate (PC), polyethylene (PE), PET (doped PE), PET-G (derivative of PE), Teslin™, Paper or Cotton/Noil, and the like.
An antenna, which may be referred to as a “card antenna” (CA), may be mounted to the inlay substrate using a sonotrode (ultrasonic tool) and electrically connected with the chip module (CM). See, for example U.S. Pat. No. 6,698,089 and U.S. Pat. No. 6,233,818, incorporated by reference herein. A typical pattern for a card antenna (CA) is generally rectangular, in the form of a flat (planar) coil (spiral) having a number of turns, disposed around the periphery of the substrate (or relevant portion thereof). See, for example, U.S. Pat. No. 7,980,477 (2011, Finn).
Rather than directly electrically connecting the RFID chip (CM) to a card antenna (CA), a module antenna (MA) may be incorporated into an antenna module (AM) comprising the RFID chip (CM) and the module antenna (MA). The module antenna (MA) may be quite small (such as approximately 15 mm×15 mm), in contrast with the card antenna (CA) (such as approximately 50 mm×80 mm). The module antenna (MA) may be inductively coupled rather than electrically connected to the card antenna (CA). In such cases, the card antenna (CA) may be referred to as a booster antenna (BA). The booster antenna (BA) may comprise a portion disposed around the periphery of the card body (CB), and another portion which may comprise a coupler coil (CC) disposed at an interior area of the card body (CB) for inductively coupling with the module antenna (MA). The terms card antenna (CA) and booster antenna (BA) may be used interchangeably herein.
US 20120038445 (2012, Finn) discloses a transponder with an antenna module (AM) having a chip module (CM) and an antenna (MA); a booster antenna (BA) having outer and inner antenna structures (D,E) in the form of flat coils disposed around the periphery of the card body (CB). The antenna module (AM) may be positioned so that its antenna (MA) overlaps only one of the antenna structures or the second antenna structure, for inductive coupling thereto.
U.S. Pat. No. 5,084,699 (1992, Trovan) entitled Impedance Matching Coil Assembly For An Inductively Coupled Transponder. Attention is directed to FIG. 5. A coil assembly for use in an inductively powered transponder includes a primary coil (156) and a secondary coil (158) wrapped around the same coil forming ferrite rod (160). The primary coil's leads (162) are left floating while the secondary coil's leads (164) are connected to the integrated identification circuit of the transponder.
U.S. Pat. No. 5,955,723 (1999, Siemens) entitled Contactless Chip Card discloses a data carrier configuration includes a semiconductor chip. Attention is directed to FIG. 1. A first conductor loop (2) is connected to the semiconductor chip (1) and has at least one winding and a cross-sectional area with approximately the dimensions of the semiconductor chip. At least one second conductor loop (3) has at least one winding, a cross-sectional area with approximately the dimensions of the data carrier configuration and a region forming a third loop (4) with approximately the dimensions of the first conductor loop (2). The third loop (4) inductively couples the first conductor loop (2) and the at least one second conductor loop (3) to one another.
U.S. Pat. No. 6,378,774 (2002, Toppan) discloses a smart card comprising an IC module and an antenna for non-contact transmission. The IC module has both a contact-type function and a non-contact-type function. The IC module has a first coupler coil (8), the antenna has a second coupler coil (3). The first and second coupler coils are disposed to be closely coupled to each other, and are coupled in a non-contact state by transformer coupling. Various ways of forming the first coupler coil (8) are shown. For example, in FIG. 14, the first coupler coil (8) is wound around a coil frame (17), which is provided around the seal resin (16) of IC chip (6).
U.S. Pat. No. 7,928,918 (2011, Gemalto) entitled Adjusting Resonance Frequency By Adjusting Distributed Inter-Turn Capacity discloses a method for adjusting frequency tuning of a resonant circuit with turns having a regular spacing generating stray inter-turn capacity.
U.S. Pat. No. 8,130,166 (2012, Assa Abloy) discloses Coupling Device For Transponder And Smart Card With Such Device. Attention is directed to FIG. 6. A coupling device is formed by a continuous conductive path having a central section (12) and two extremity sections (11, 11′), the central section (12) forming at least a small spiral for inductive coupling with the transponder device, the extremities sections (11, 11′) forming each one large spiral for inductive coupling with the reader device.
US2010/0176205 (2010, SPS) entitled Chip Card With Dual Communication Interface. Attention is directed to FIG. 4. A card body (22) includes a device (18) for concentrating and/or amplifying electromagnetic waves, which can channel the electromagnetic flow received, in particular, from a contactless chip card reader toward the coils of the antenna (13) of the microelectronic module (11). The device (18) for concentrating and/or amplifying electromagnetic waves may consist of a metal sheet disposed in the card body (22) below the cavity (23) receiving the microelectronic module (11), or may consist of an antenna consisting of at least one coil, disposed in the card body (22) below the cavity (23) receiving the microelectronic module (11).
The following patents and publications are referenced, and may be “incorporated by reference”, herein: CA 2,279,176 (1998, PAV); DE 39 35 364 (1990, ADE); DE 43 11 493 (2000, Amatech); NL 9100347 (1992, ‘Nedap’); U.S. Pat. No. 5,773,812 (1998, ADE); U.S. Pat. No. 6,008,993 (1999, ADE); U.S. Pat. No. 6,142,381 (2000, Finn et al.); U.S. Pat. No. 6,190,942 (2001, “PAV”); U.S. Pat. No. 6,095,423 (2000, Siemens); U.S. Pat. No. 6,310,778 (2001, Finn et al.); U.S. Pat. No. 6,406,935 (2002, ASK); U.S. Pat. No. 6,719,206 (2004, On Track); U.S. Pat. No. 7,320,738 (2008, FCI); U.S. Pat. No. 8,100,337 (2012, “SPS”); US 2008/0283615 (2008, Finn); US 2008/0308641 (2008, Finn); US 2008/0314990 (2008, Smartrac); US 20090057414; US 2002/0020903 (2002, ADE); US 20100283690 (2010, SPS); US 2011/0163167 (2011, SPS).